We intend to investigate the mechanism of chemoreception using the marine gastropod Aplysia as a model system. In a series of behavioral experiments, attempts will be made to identify effective molecules from materials that elicit distinct stereotyped responses such as food searching, feeding, escape and mating behavior in Aplysia, and to determine the location and threshold of chemoreceptors that are responsive to these stimuli. Electrophysiological techniques will be used: a) to identify and map the central neurons that respond to chemical stimulation of the animal; b) to examine the range and spectrum of sensitivity of individual identified neurons to a group of natural and other chemosensory stimuli; and c) to study the neuronal and across-neuronal patterns of activity produced by the chemosensory stimuli in the identified neurons. Attempts will also be made to investigate the interconnections of these cells and the efferent connections of neurons responsive to stimuli which produce distinct behavioral effects such as feeding response. It is hoped that the results of the proposed experiments on the chemosensory system of Aplysia will help us to understand: 1) how different chemosensory stimulus qualities are represented in the afferent neural activity; 2) how chemosensory information is processed in the central nervous system, and 3) what central events finally determine the specific behavioral response to a particular chemosensory stimulus.